Performance Comparison of HMA Mixes Used on Different Levels of North Dakota’s Highway Performance Classification System

There are five levels of the Highway Performance Classification System (HPCS) in North Dakota: Interstate, Interregional, State Corridor, District Corridor, and District Collector. This study’s main objective is to compare the performance of hotmix asphalt (HMA) mixes used for different levels of the HPCS in terms of fatigue cracking, low-temperature cracking, rutting, and moisture sensitivity. The HMA field mixes were collected from seven of the eight districts in North Dakota. HMA mixes were compacted using the superpave gyratory compactor (SGC) at 7 ± 0.5% air voids. The resistance of these mixtures to low-temperature cracking, fatigue cracking, rutting, and moisture damage was determined using disc-shaped compact tension (DCT), semi-circular bend (SCB), asphalt pavement analyzer (APA), and indirect tensile test (IDT), respectively. For each of the 19 projects in this study, at least three specimens were analyzed for low-temperature and fatigue cracking, and four specimens were analyzed for rutting. Six specimens in each of the seven districts included in the study were tested to obtain data on moisture damage resistance. Performance specifications of rut depth for rutting resistance, flexibility index (FI) for fatigue cracking resistance, and fracture energy for low-temperature cracking resistance were determined based on test results and literature reviews. All asphalt mixes met the rut depth criteria, and some of the mixes used on State and District Corridors did not meet the fatigue or low-temperature cracking performance specifications set for this study.